We hear Jennifer Siebel, the actress wife of San Francisco mayor Gavin Newsom, is pregnant — and furious with the friends who let word slip. But we bet her pro-gay marriage husband is thrilled.

Newsom, a Democrat, has declared himself a candidate for California's governor seat, a wide-open race taking place next year, since term limits are keeping Arnold Schwarzenegger from running again. A rising star in the Democratic party, Newsom has hurt himself with gaffes both personal and political.

He and his first wife, Fox News TV host kimberly Guilfoyle, divorced in 2006. While going through the divorce, Newsom had an affair with Ruby Rippey-Tourk, the wife of his campaign manager, Alex Tourk. The divorce and affair ruined Newsom's Camelot-by-the-Bay image.

His wedding last year to Siebel, a cousin of wealthy software entrepreneur Tom Siebel, was a step towards restoring his tattered image. (Google founders Larry Page and Sergey Brin ferried guests in their private jet to the wedding site on a Montana ranch.)

But then came Proposition 8, California's ban on gay marriage, a cause Newsom has championed since he defied state law in 2004 by issuing marriage licenses to gay couples (including the author of this post). At a rally, Newsom declared that gay marriage was coming to California "whether you like it or not," a sound bite Prop 8 supporters aired endlessly in TV commercials and was cited in many election post-mortems as a factor in the passage of Prop 8.

With memories of his messy personal life still fresh, and his main cause defeated in the last state election, Newsom's push for the governor's seat looked like it was off to a rocky start. In the Democratic primary, he faces California Attorney General Jerry Brown, the former Governor Moonbeam.

But political observers say Brown may strike potential voters as too old. With Newsom's wife expecting a child in the fall, he will have the perfect family-man campaign prop. What better way for a claimant to the throne to seem young and vital than to have his very own heir?

Update: The mayor's office has confirmed that the Newsoms are expecting. Spokesman Nathan Ballard said:

We are pleased to confirm that Mayor Gavin Newsom and First Lady Jennifer Siebel Newsom are starting a family. The Mayor and the First Lady are thrilled to be embarking on this adventure together, and they appreciate your good wishes.